Conversion of a direct current (DC) power supply voltage to a different voltage is employed for various purposes, including for example charging batteries or providing power to selected components within a computer, mobile telephone, or other electronic device. A versatile DC-DC controller should operate as either a “buck” (step-down) controller or a “boost” (step-up) controller, depending on the specific needs of the application, and should preferably operate across a complete range of input-output conversions without discontinuities. However, when changing a power supply voltage to a voltage that is close to that of the power supply, conversion efficiency (the power retained after conversion—that is, the input power less conversion losses) can be unacceptably low.
There is, therefore, a need in the art for an improved DC-DC controller with high efficiency even when generating a desired output voltage that is close to the input voltage.